Biofeedback apparatus
In biofeedback there are a number of pieces of apparatus that can be used. These include: Capnometer A capnometer or capnograph uses an infrared detector to measure end-tidal (the partial pressure of carbon dioxide in expired air at the end of expiration) exhaled through the nostril into a latex tube. The average value of end-tidal for a resting adult is 5% ( ). A capnometer is a sensitive index of the quality of patient breathing. Shallow, rapid, and effortful breathing lowers , while deep, slow, effortless breathing increases it. Biofeedback therapists use capnometric biofeedback to supplement respiratory strain gauge biofeedback with patients diagnosed with anxiety disorders, asthma, chronic pulmonary obstructive disorder (COPD), essential hypertension, panic attacks, and stress.Fried, R. (1993). The psychology and physiology of breathing. New York: Plenum Press. Electromyograph An electromyograph (EMG) uses surface electrodes to detect muscle action potentials from underlying skeletal muscles that initiate muscle contraction. Clinicians record the surface electromyogram (SEMG) using one or more active electrodes that are placed over a target muscle and a reference electrode that is placed within six inches of either active. The SEMG is measured in microvolts (millionths of a volt).Tassinary, L. G., Cacioppo, J. T., & Vanman, E. J. (2007). The skeletomotor system: Surface electromyography. In J. T. Cacioppo, L. G. Tassinary, & G. G. Berntson, (Eds.). Handbook of psychophysiology (3rd ed.). New York: Cambridge University Press.Florimond, V. (2009). Basics of surface electromyography applied to physical rehabilitation and biomechanics. Montreal: Thought Technology Ltd. Biofeedback therapists use EMG biofeedback when treating anxiety and worry, chronic pain, computer-related disorder, essential hypertension, headache (migraine, mixed headache, and tension-type headache), low back pain, physical rehabilitation (cerebral palsy, incomplete spinal cord lesions, and stroke), temporomandibular joint disorder (TMD), torticollis, and fecal incontinence, urinary incontinence, and pelvic pain. Feedback thermometer A feedback thermometer detects skin temperature with a thermistor (a temperature-sensitive resistor) that is usually attached to a finger or toe and measured in degrees Celsius or Fahrenheit. Skin temperature mainly reflects arteriole diameter. Hand-warming and hand-cooling are produced by separate mechanisms, and their regulation involves different skills.Andreassi, J. L. (2007). Psychophysiology: Human behavior and physiological response (5th ed.). Hillsdale, NJ: Lawrence Erlbaum and Associates, Inc. Hand-warming involves arteriole vasodilation produced by a beta-2 adrenegeric hormonal mechanism.Cohen, R. A., & Coffman, J. D. (1981). Beta-adrenergic vasodilator mechanism in the finger, Circulation Research, 49, 1196-1201] Hand-cooling involves arteriole vasoconstriction produced by the increased firing of sympathetic C-fibers. Biofeedback therapists use temperature biofeedback when treating chronic pain, edema, headache (migraine and tension-type headache), essential hypertension, Raynaud’s disease, anxiety, and stress. Electrodermograph An electrodermograph (EDG) measures skin electrical activity directly (skin conductance and skin potential) and indirectly (skin resistance) using electrodes placed over the digits or hand and wrist. Orienting responses to unexpected stimuli, arousal and worry, and cognitive activity can increase eccrine sweat gland activity, increasing the conductivity of the skin for electrical current. In skin conductance, an electrodermograph imposes an imperceptible current across the skin and measures how easily it travels through the skin. When anxiety raises the level of sweat in a sweat duct, conductance increases. Skin conductance is measured in microsiemens (millionths of a siemens). In skin potential, a therapist places an active electrode over an active site (e.g., the palmar surface of the hand) and a reference electrode over a relatively inactive site (e.g., forearm). Skin potential is the voltage that develops between eccrine sweat glands and internal tissues and is measured in millivolts (thousandths of a volt). In skin resistance, also called galvanic skin response (GSR), an electrodermograph imposes a current across the skin and measures the amount of opposition it encounters. Skin resistance is measured in kΩ (thousands of ohms).Dawson, M. E., Schell, A. M., & Filion, D. L. (2007). The electrodermal system. In J. T. Cacioppo, L. G. Tassinary, & G. G. Berntson (Eds.). Handbook of psychophysiology (3rd) ed.). New York: Cambridge University Press. Biofeedback therapists use electrodermal biofeedback when treating anxiety disorders, hyperhidrosis (excessive sweating), and stress.Moss, D. (2003). The anxiety disorders. In D. Moss, D., A. McGrady, T. Davies, & I. Wickramasekera (Eds.), Handbook of mind-body medicine in primary care (pp. 359-375). Thousand Oaks, CA: Sage. Electrodermal biofeedback is used as an adjunct to psychotherapy to increase client awareness of their emotions. In addition, electrodermal measures have long served as one of the central tools in polygraphy (lie detection) because they reflect changes in anxiety or emotional activation. Electroencephalograph An electroencephalograph (EEG) measures the electrical activation of the brain from scalp sites located over the human cortex. The EEG shows the amplitude of electrical activity at each cortical site, the amplitude and relative power of various wave forms at each site, and the degree to which each cortical site fires in conjunction with other cortical sites (coherence and symmetry).Kropotov, J. D. (2009). Quantitative EEG, event-related potentials and neurotherapy. San Diego, CA: Academic Press. The EEG uses precious metal electrodes to detect a voltage between at least two electrodes located on the scalp. The EEG records both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) that largely occur in dendrites in pyramidal cells located in macrocolumns, several millimeters in diameter, in the upper cortical layers. Neurofeedback monitors both slow and fast cortical potentials.Thompson, M., & Thompson, L. (2003). The biofeedback book: An introduction to basic concepts in applied psychophysiology. Wheat Ridge, CO: Association for Applied Psychophysiology and Biofeedback. Slow cortical potentials are gradual changes in the membrane potentials of cortical dendrites that last from 300 ms to several seconds. These potentials include the contingent negative variation (CNV), readiness potential, movement-related potentials (MRPs), and P300 and N400 potentials.Stern, R. M., Ray, W. J., & Quigley, K. S. (2001). Psychophysiological recording (2nd ed.). New York: Oxford University Press. Fast cortical potentials range from 0.5 Hz to 100 Hz.LaVaque, T. J. (2003). Neurofeedback, Neurotherapy, and quantitative EEG. In D. Moss, A. McGrady, T. Davies, & I. Wickramasekera (Eds), Handbook of mind-body medicine for primary care (pp. 123-136). Thousand Oaks, CA: Sage. The main frequency ranges include delta, theta, alpha, the sensorimotor rhythm, low beta, high beta, and gamma. The specific cutting points defining the frequency ranges vary considerably among professionals. Fast cortical potentials can be described by their predominant frequencies, but also by whether they are synchronous or asynchronous wave forms. Synchronous wave forms occur at regular periodic intervals, whereas asynchronous wave forms are irregular. The synchronous delta rhythm ranges from 0.5 to 3.5 Hz. Delta is the dominant frequency from ages 1 to 2, and is associated in adults with deep sleep and brain pathology like trauma and tumors, and learning disability. The synchronous theta rhythm ranges from 4 to 7 Hz. Theta is the dominant frequency in healthy young children and is associated with drowsiness or starting to sleep, REM sleep, hypnagogic imagery (intense imagery experienced before the onset of sleep), hypnosis, attention, and processing of cognitive and perceptual information. The synchronous alpha rhythm ranges from 8 to 13 Hz and is defined by its waveform and not by its frequency. Alpha activity can be observed in about 75% of awake, relaxed individuals and is replaced by low-amplitude desynchronized beta activity during movement, complex problem-solving, and visual focusing. This phenomenon is called alpha blocking. The synchronous sensorimotor rhythm (SMR) ranges from 12 to 15 Hz and is located over the sensorimotor cortex (central sulcus). The sensorimotor rhythm is associated with the inhibition of movement and reduced muscle tone. The beta rhythm consists of asynchronous waves and can be divided into low beta and high beta ranges (13–21 Hz and 20–32 Hz). Low beta is associated with activation and focused thinking. High beta is associated with anxiety, hypervigilance, panic, peak performance, and worry. EEG activity from 36 to 44 Hz is also referred to as gamma. Gamma activity is associated with perception of meaning and meditative awareness.Steriade, M. (2005). Cellular substrates of brain rhythms. In E. Niedermeyer and F. Lopes da Silva (Eds.). Electroencephalography: Basic principles, clinical applications, and related fields (5th ed.). Philadelphia: Lippincott Williams & Wilkins.Shaffer, F., & Moss, D. (2006). Biofeedback. In C. S. Yuan, E. J. Bieber, & B.A. Bauer (Ed.), Textbook of complementary and alternative medicine (2nd ed.) (pp. 291-312). Abingdon, Oxfordshire, UK: Informa Healthcare. Neurotherapists use EEG biofeedback when treating addiction, attention deficit hyperactivity disorder (ADHD), learning disability, anxiety disorders (including worry, obsessive-compulsive disorder and posttraumatic stress disorder), depression, migraine, and generalized seizures.T. H. Budzynski, H. K. Budzynski, J. R. Evans, & A. Abarbanel (Eds.) (2009). Introduction to quantitative EEG and neurofeedback (2nd ed.). Burlington, MA: Academic Press. Photoplethysmograph A photoplethysmograph (PPG) measures the relative blood flow through a digit using a photoplethysmographic (PPG) sensor attached by a Velcro band to the fingers or to the temple to monitor the temporal artery. An infrared light source is transmitted through or reflected off the tissue, detected by a phototransistor, and quantified in arbitrary units. Less light is absorbed when blood flow is greater, increasing the intensity of light reaching the sensor.Combatalade, D. (2009). Basics of heart rate variability applied to psychophysiology. Montreal, Canada: Thought Technology Ltd. A photoplethysmograph can measure blood volume pulse (BVP), which is the phasic change in blood volume with each heartbeat, heart rate, and heart rate variability (HRV), which consists of beat-to-beat differences in intervals between successive heartbeats.Lehrer, P. M. (2007). Biofeedback training to increase heart rate variability. In P. M. Lehrer, R. M. Woolfolk, & W. E. Sime (Eds.). Principles and practice of stress management (3rd ed.). New York: The Guilford Press. A photoplethysmograph can provide useful feedback when temperature feedback shows minimal change. This is because the PPG sensor is more sensitive than a thermistor to minute blood flow changes. Biofeedback therapists can use a photoplethysmograph to supplement temperature biofeedback when treating chronic pain, edema, headache (migraine and tension-type headache), essential hypertension, Raynaud’s disease, anxiety, and stress. Electrocardiograph The electrocardiograph (ECG) uses electrodes placed on the torso, wrists, or legs, to measure the electrical activity of the heart and measures the interbeat interval (distances between successive R-wave peaks in the QRS complex). The interbeat interval, divided into 60 seconds, determines the heart rate at that moment. The statistical variability of that interbeat interval is what we call heart rate variability.Berntson, G. G., Quigley, K. S., & Lozano, D. (2007). Cardiovascular psychophysiology. In J. T. Cacioppo, L. G. Tassinary, & G. G. Berntson, (Eds.). Handbook of psychophysiology (3rd ed.). New York: Cambridge University Press. The ECG method is more accurate than the PPG method in measuring heart rate variability.Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (1996). Heart rate variability: Standards of measurement, physiological interpretation, and clinical use. Circulation, 93, 1043-1065. Biofeedback therapists use HRV biofeedback when treating asthma, COPD, depression, fibromyalgia, heart disease, and unexplained abdominal pain. Pneumograph A pneumograph or respiratory strain gauge uses a flexible sensor band that is placed around the chest, abdomen, or both. The strain gauge method can provide feedback about the relative expansion/contraction of the chest and abdomen, and can measure respiration rate (the number of breaths per minute). Clinicians can use a pneumograph to detect and correct dysfunctional breathing patterns and behaviors. Dysfunctional breathing patterns include clavicular breathing (breathing that primarily relies on the external intercostals and the accessory muscles of respiration to inflate the lungs), reverse breathing (breathing where the abdomen expands during exhalation and contracts during inhalation), and thoracic breathing (shallow breathing that primarily relies on the external intercostals to inflate the lungs). Dysfunctional breathing behaviors include apnea (suspension of breathing), gasping, sighing, and wheezing.Peper, E., Tylova, H., Gibney, K. H., Harvey, R., & Combatalade, D. (2008). Biofeedback mastery: An experiential teaching and self-training manual. Wheat Ridge, CO: Association for Applied Psychophysiology and Biofeedback. A pneumograph is often used in conjunction with an electrocardiograph (ECG) or photoplethysmograph (PPG) in heart rate variability (HRV) training. Biofeedback therapists use pneumograph biofeedback with patients diagnosed with anxiety disorders, asthma, chronic pulmonary obstructive disorder (COPD), essential hypertension, panic attacks, and stress.Fried, R. (1987). The hyperventilation syndrome: Research and clinical treatment. Baltimore: Johns Hopkins University Press. Rheoencephalograph Rheoencephalography (REG), or brain blood flow biofeedback, is a biofeedback technique of a conscious control of blood flow. An electronic device called a rheoencephalograph Greek rheos stream, anything flowing, from rhein to flow is utilized in brain blood flow biofeedback. Electrodes are attached to the skin at certain points on the head and permit the device to measure continuously the electrical conductivity of the tissues of structures located between the electrodes. The brain blood flow technique is based on non-invasive method of measuring bio-impedance. Changes in bio-impedance are generated by blood volume and blood flow and registered by a rheographic device.Tokarev V.E. "A Rheoencephalogram (REG) Variability System Based on ISKRA-226 Personal Computer", Institute for Complex Problem of Hygiene Healthcare Conference, Novokuznetsk, Russia, 1989, p.115-116. The pulsative bio-impedance changes directly reflect the total blood flow of the deep structures of brain due to high frequency impedance measurements.Tokarev V.E. "Regulatory Mechanisms of Physiological Systems During REG Biofeedback", 25th Annual Meeting of Association of Applied Psychophysiology and Biofeedback, Atlanta, USA, 1994 Hemoencephalograph Hemoencephalography or HEG biofeedback is a functional infrared imaging technique. As its name describes, it measures the differences in the color of light reflected back through the scalp based on the relative amount of oxygenated and unoxygenated blood in the brain. Research continues to determine its reliability, validity, and clinical applicability. HEG is used to treat ADHD and migraine, and for research.Toomim, H., & Carmen, J. (2009). Homoencephalography: Photon-based blood flow neurofeedback. In T. H. Budzynski, H. K. Budzynski, J. R. Evans, & A. Abarbanel (Eds.) (2009). Introduction to quantitative EEG and neurofeedback (2nd ed.). Burlington, MA: Academic Press. References